Step 1

Process flour, butter, yeast and rind in a food processor until fine crumbs form. Add sour cream, milk and yolk, pulse until a soft dough forms (1-2 minutes), then turn onto a lightly floured surface and knead until very smooth (1-2 minutes). Place in a lightly buttered bowl, cover and stand until slightly risen (30 minutes). Knock down dough, knead on a lightly floured surface and stand until slightly risen (30 minutes).

Step 2

Meanwhile, for poppy-seed filling, process poppy seeds in a small food processor or coffee grinder to grind, transfer to a saucepan and add remaining ingredients. Stir continuously over medium-high heat until boiling, reduce heat to medium and simmer, stirring continuously, until thick and smooth (12-15 minutes). Cool completely.

Step 3

Preheat oven to 220C. Divide dough into two, and roll out each piece on a lightly floured surface into a 20cm x 30cm rectangle. Spread half the poppy-seed filling over each piece leaving a 3cm-border, then, with shortest side facing you, roll into a cylinder. Place each cylinder, seam-side down, on a baking tray lined with baking paper, brush with eggwash, stand until risen (1 hour). Bake for 10 minutes, reduce oven to 180C and bake until golden and cooked through (15-20 minutes). Serve warm or cool, dusted with icing sugar. Scrolls will keep, stored in an airtight container, for 2 weeks.